An ultra-high-strength screw is known from European patent application EP 2 594 653 A1 corresponding to U.S. Pat. No. 9,145,910 B2.
A high-strength screw is known from U.S. Pat. No. 3,301,120. The threaded portion of the screw is tempered such that it has a reduced hardness compared to the inner core of the screw.
A screw is known from German patent application No. DE 10 2014 220 338 A1. The screw is a hybrid screw consisting of two different materials. The screw includes an inner core being made of a harder material such as a high-strength aluminum alloy. The cover material is different and may be aluminum, aluminum alloy, magnesium, magnesium alloy, copper or copper alloy.
Another hybrid screw being made of different materials is known from German patent No. DE 10 2007 000 485 B3 corresponding to U.S. Pat. No. 7,824,142 B2.